DE102011082688B4 - FET relay and test module for testing electrically controllable circuit breakers - Google Patents

Abstract

FET relay having an optocoupler (30) as a control circuit and a FET switching stage (40) as a load circuit, which comprises two FET switching transistors (42, 44), wherein the optocoupler (30) has a coupling stage (32), which in dependence from an on the coupling stage (32) applied control signal (U _S ) an output driver (34) for driving the FET switching stage (40) drives, characterized by an energy store (E _S1 ) for powering the output driver (34) of the optocoupler (30) which, in order to reduce the turn-on times, quickly charges gate capacitances of the FET switching transistors (42, 44) of the FET switching stage (40) via the output driver (34) designed as a push-pull output stage, the output driver (34) of the opto-coupler (30) designed as a push-pull output stage ) quickly discharges the gate capacitances of the FET switching transistors (42, 44) of the FET switching stage (40).

Description

State of the art

The invention relates to a FET relay according to the preamble of independent claim 1 and of a test module for testing electrically controllable circuit breakers, which are used in particular for the control of personal protection means, according to the preamble of independent claim 6.

The peculiarity of the control of ignition circuits in personal protection devices lies in the energization of small ohmic loads in the ignition elements over longer cable distances and the associated physical requirements. Currently, separate functional modules are used to test or check the ignition circuits for personal protective equipment such as airbags. In this case, the function modules simulate, for example, an ohmic resistance wire of a conventional ignition element by means of a resistor decade connected via relays with a high power loss. In addition, short-circuits to selectable reference potentials, ignition circuit breaks, etc. can be emulated via relays. In addition, a set resistance of the decade can be used as a measuring resistor for ignition current measurement. Furthermore, the value of the set resistance can be displayed or output via a corresponding output unit.

In the published application DE 10 2007 044 345 A1 For example, a circuit and a method for testing electrically controllable circuit breakers for controlling personal protection means are described. For the test, an ignition element is simulated in that a resistance value of this simulation can be changed by correspondingly controlling the simulation module. As a result, the dynamic behavior of an ignition element during energization can be simulated to control the personal protection means. Various transistor types such as bipolar and / or field effect transistors (FET) or other components such as thyristors, triacs, IGBT or so-called solid state relays are proposed as electrically controllable circuit breakers, which can withstand the currents required to energize the personal protection means. The components used should have a very low forward resistance in the range of a few milli-ohms (mΩ). Logic gates, programmable modules, function generators, microcontrollers and optocouplers are proposed for floating control of the circuit breakers. In the application described, active and passive switching states have a time duration in the range from 100µs +/- 80µs or 200µs +/- 50µs. Shorter phases in the area are not planned.

Disclosure of the invention

The FET relay according to the invention with the features of independent claim 1 has the advantage that turn-on and / or turn-off can be realized under a microsecond. Due to the special structure of the FET relay according to the invention, it is also possible to switch AC voltage loads. By selecting a suitable optocoupler, which can quickly charge the gate capacitances of the output stage transistors, it is possible currents in the two-digit ampere with a very low on-resistance of about 15 mΩ and very short turn-on and / or turn-off times in the range of less than 1 μs represent. The optocoupler is used for potential separation between a control circuit and a load circuit. The potential separation of the load circuit and control circuit makes it possible, just as with electromechanical relays or solid-state relays, to arrange several FET relays in any combination.

Embodiments of the present invention can advantageously replace electromechanical relays and / or semiconductor relays (solid-state relays) in order to be able to emulate extremely short interruptions and / or low-resistance short circuits on any electrically controllable circuit breakers, which are used in particular for personal protection devices. In addition, the FET relay according to the invention enables a higher measurement accuracy through reproducible, aging-stable and low switch transition resistances as well as reproducible switching times in contrast to conventional switching relays, which have varying bounce times and an age-related variance of the switch contact resistances. Furthermore, the FET relay according to the invention results in a reduced energy requirement due to the reduction in the relay control currents.

The basic idea of the present invention is that an energy store is used in order to be able to charge the gate capacitances of the FET switching transistors of the FET switching stage quickly via the output driver in order to be able to implement the short switch-on times. At the same time, the output driver is designed as a push-pull output stage in order to be able to quickly discharge the gate capacitances of the FET switching transistors of the FET switching stage in order to reduce the switch-off times.

Embodiments of the present invention provide a FET relay having an optical coupler as a control circuit and a FET switching circuit as a load circuit comprises two FET switching transistors. The optocoupler has a coupling stage, which activates an output driver for driving the FET switching stage as a function of a control signal applied to the coupling stage. According to the invention, an energy storage device for powering the output driver of the opto-coupler is present, which rapidly charges gate capacitances of the FET switching transistors of the FET switching stage via the output driver designed as a push-pull output driver in order to reduce the switch-on times, wherein the push-pull output driver of the optocoupler executes the gate capacitances of the FET switching transistor FET switching stage quickly discharges to reduce the turn-off. The FET switching transistors may be implemented as N-channel field-effect transistors or P-channel field-effect transistors, but are preferably designed as N-channel field-effect transistors due to the power class.

Preferably, embodiments of the present invention may be used to verify the LV124 specification for personal security ignition circuitry.

Embodiments of the FET relay according to the invention can be used for example in a test module for testing electrically controllable circuit breakers, which are used in particular for driving personal protection means. Such a test module comprises an evaluation and control unit, a measurement unit and a replica assembly. In this case, the evaluation and control unit controls the replica assembly in response to outputs of the measurement unit and test specifications to set certain electrical properties at test leads of the replica assembly. The replica assembly comprises at least one FET relay according to the invention for adjusting the electrical properties at the test connections. By the evaluation and control unit, which is preferably designed as a microcontroller, results in an advantageous manner a functional extension in the control of the test module for the review of different ignition circuits for personal protection. In addition, the possibility of multiple use of hardware circuits for different functions can result from a corresponding configuration and parameterization. Furthermore, a shift of complex functionality from a higher-level test software to the low-level level in the test module may result. This allows a simplification of software maintenance. In addition, new test functions can be introduced and thus a higher test depth can be achieved when checking the personal protection equipment.

Thus, for example, any number of FET relays according to the invention can be used as switching elements in a high-load resistor decade in order to be able to make rapid changes in resistance.

The measures and refinements recited in the dependent claims advantageous improvements of the independent claim 1 specified FET relay and the test module specified in the independent claim 6 are possible.

It is particularly advantageous that output terminals of the FET relay can be connected to a load circuit independent of polarity. For this purpose, the source terminals of the two FET switching transistors are connected to each other and provide a common reference potential, wherein the gate terminals of the two FET switching transistors are connected to each other and simultaneously driven by the output driver, and wherein the drain terminals the two FET switching transistors each form an output terminal of the FET relay. Therefore, the load circuit supply voltage can be reversed in an advantageous manner. In addition, AC loads can also be switched.

In an advantageous embodiment of the FET relay according to the invention, the energy storage and / or the optocoupler and / or the FET switching stage can be dimensioned so that at the output of the FET relay at a switch-on the on-time delay is in the range of 250 to 350ns, and the turn-off delay is in the range of 450 to 550ns, and the rise time is in the range of 80 to 120ns, and the fall time is in the range of 70 to 90ns. In addition, the energy storage and / or the optocoupler and / or the FET switching stage can be dimensioned so that at the output of the FET relay at an off pulse, the on-time delay and the off-time delay in the range of 450 to 550ns, and the rise time in the range of 80 to 120ns, and the fall time is in the range of 70 to 90ns.

In an advantageous embodiment of the test module according to the invention, each FET relay can be combined with a pulse generator to form a switching unit, the pulse generator generating a control voltage as a function of a control signal with a predetermined time profile for actuating the FET relay. The pulse generator outputs the desired pulse shape. In addition, the pulse generator can comprise an amplifier stage in order to minimize the required drive power. Series resistors with appropriate dimensions can also be provided in order to be able to control the FET relay with other voltage levels.

In a further advantageous embodiment of the test module according to the invention, a first switching unit can bridge a predetermined simulation resistor or loop into a signal path between the two test connections of the test module or disconnect the signal path between the two test connections of the test module. A second switching unit can insert a minimum resistance value or a maximum resistance value in a signal path between the two test connections, the minimum resistance corresponding to a drain-source resistance of the FET switching transistors in the conductive state, and the maximum resistance corresponding to a drain-source resistance corresponds to the FET switching transistors in the blocking state. A third switching unit can connect a first test connection to a first reference potential and / or a fourth switching unit can connect the first test connection to a second reference potential and / or a fifth switching unit can connect a second test connection to a third reference potential and / or a sixth switching unit can Connect the second test connection to a fourth reference potential. The various switching units can be used to advantageously simulate the real properties of ignition circuits for personal protection devices. For example, an adjustable high-load resistance decade can be displayed to simulate resistances in airbag ignition circuits and / or configurable switch-on times and / or switch-off times can be made available, which can be set using time or voltage criteria in order to be able to simulate real behavior of airbag ignition circuits , In addition, short circuits or shunts of the output connections to different potentials can be realized. Interruptions with an adjustable duration can be specified to simulate bounce behavior and loose contacts.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. In the drawings, like reference numerals designate components that perform the same or analog functions.

list of figures

• 1 shows a schematic block diagram of an embodiment of a test module for testing electrical circuit breakers for controlling personal protection devices in a motor vehicle, which has at least one FET relay according to the invention.
• 2 shows a schematic block diagram of an embodiment of a replica assembly having at least one inventive FET relay for the test module 1 ,
• 3 shows a schematic block diagram of an embodiment of a switching unit, which has at least one FET relay according to the invention, for the replica assembly 2 ,
• 4 shows a schematic block diagram of an embodiment of a pulse generator for the switching unit 3 for generating a drive voltage for the FET relay.
• 5 shows a schematic block diagram of an embodiment of a DC / DC converter for the switching unit 3 for generating a second supply voltage for the FET relay.
• 6 to 11 show characteristics of control voltage curves at the input of the FET relay 3 and corresponding measuring voltage curves at the output of the FET relay 3 ,

Embodiments of the invention

How out 1 can be seen includes the illustrated embodiment of a test module according to the invention 1 for testing electrically controllable circuit breakers, which are used for driving personal protection means, an evaluation and control unit 3 , a measurement unit 5 and a replica assembly 10 , This is controlled by the evaluation and control unit 3 the replica assembly 10 depending on outputs of the measuring unit 5 and from test specifications to determine certain electrical properties at test terminals HS, LS of the replica assembly 10 adjust. The two test connections HS, LS are connected to corresponding terminals of the circuit breaker to be tested.

How out 1 it can also be seen that the individual components of the test module communicate 1 via a common bus system 2 , There is also an input unit 7 and an output unit 9 provided as a human-machine interface to operate the test module 1 and to enable the test results to be output. The test module also includes 1 a TTL output unit 4 , which provides a digital TTL output signal as a trigger signal for subsequent functions if required. The trigger signal is preferably synchronized with a starting edge of an ignition pulse for a personal protection device.

How out 2 can be seen, includes the replica assembly 10 several switching units 12.0 . 12.1 . 12.n . 14.1 . 14.2 . 15 . 16.1 . 16.2 to simulate real properties of ignition circuits for personal protection devices and to check the control circuit to be tested connected to the test connections HS and LS. In 2 was for the sake of clarity on the representation of the lines for the transmission of control signals S1 for the switching units 12.0 . 12.1 . 12.n . 14.1 . 14.2 . 15 . 16.1 . 16.2 waived. Each of the switching units 12.0 . 12.1 . 12.n . 14.1 . 14.2 . 15 . 16.1 . 16.2 however, has at least one control signal S1 from the evaluation and control unit 3 controlled, the evaluation and control unit 3 for the transmission of the control signals S1 preferably the bus system 2 used. The test module also has two measuring connections M1 . M2 on between which a measuring resistor 5.1 or measuring shunt can be looped in, which the measuring unit 5 used to measure a current flow between the two test connections HS, LS. If no current flow is to be measured, the measuring connections can be made M1 . M2 over a short circuit bridge 5.2 to be connected with each other.

How out 3 can be seen, include the switching units 12.0 . 12.1 . 12.n . 14.1 . 14.2 . 15 . 16.1 . 16.2 one pulse generator each 50 and a FET relay 20 , The respective pulse generator 50 comes with a first supply voltage U _V1 is supplied and connected to a first ground potential GND1. In addition, the respective pulse generator 50 from the evaluation and control unit 3 via the control signal S1 controlled and generates a control voltage U _S with a predetermined time course for controlling the corresponding FET relay 20 , The respective FET relay 20 includes an optocoupler 30 as a control circuit and a FET switching stage 40 as a load circuit, which two FET switching transistors 42 . 44 includes. The respective FET relay 20 comes with a second supply voltage U _V2 is supplied and is connected to a second ground potential GND2. The optocoupler 30 has a coupling stage 32 on, which depends on the at the coupling stage 32 applied control voltage U _S an output driver 34 for controlling the FET switching stage 40 controls.

According to the invention, an energy store ES1 is used to supply energy to the output driver 34 of the optocoupler 30 provided that to reduce the turn-on gate capacitances of the FET switching transistors 42 . 44 the FET switching stage 40 via the output driver 34 charges quickly. In addition, is the, output driver 34 of the optocoupler 30 designed as a push-pull output stage to rapidly discharge the gate capacitances of the FET switching transistors 42 . 44 the FET switching stage 40 to reduce switch-off times. A ceramic capacitor is preferably used as the energy store ES1, which rapidly recharges the gate capacitances of the FET switching transistors 42 . 44 allows. In the illustrated embodiment, the FET switching transistors 42 . 44 designed as N-channel field effect transistors.

The optocoupler 30 is used for electrical isolation between the control circuit and the load circuit. Due to the potential separation of the load circuit and control circuit, as with electromechanical relays or solid-state relays, several FET relays are possible 20 to be arranged in any combination.

To a polungsunabhängigen connection of any load circuit U _L at the output terminals E1 . E2 allow the respective switching stage, the two FET switching transistors 42 . 44 on the in 3 manner shown interconnected with each other.

How out 3 can also be seen, are the source connections S of the two FET switching transistors 42 . 44 connected to each other and represent a common reference potential, here a second ground potential GND2 , to disposal. In addition, the gate connections G of the two FET switching transistors 42 . 44 connected to each other and are simultaneously from the output driver designed as a push-pull output stage 34 of the optocoupler 30 driven. Furthermore, the drain connections D form the two FET switching transistors 42 . 44 one output port each E1 . E2 of the FET relay 20 , In the exemplary embodiment shown, the drain terminal D forms the first switching transistor 42 the first output port E1 of the FET relay 20 , and the drain terminal D of the second switching transistor 44 forms the second output port E2 of the FET relay 20 , Through the described connection of the two FET switching transistors 42 . 44 the load circuit supply voltage U _L can be reversed in an advantageous manner. AC loads can also be switched. About the measuring resistor shown R _M can according to the in the characteristic diagrams 7 . 9 . 11 shown measuring voltage U _M be measured, which the switching behavior of the FET switching transistors 42 . 44 depending on different in 6 . 8th . 10 time curves of the control voltage shown U _S shows.

How out 6 and 7 can be seen are the energy storage E _S1 and / or the optocoupler 30 , in particular the output driver designed as a push-pull output stage 34 of the optocoupler 30 , and / or the FET switching stage 40 preferably dimensioned so that at the exit E1 . E2 of the respective switching unit 12.0 . 12.1 . 12.n . 14.1 . 14.2 . 15 . 16.1 . 16.2 over the measuring resistor R _M at a On pulse, the on time delay is in the range of 250 to 350ns, and the off time delay is in the range of 450 to 550ns, and the rise time is in the range of 80 to 120ns, and the fall time is in the range of 70 to 90ns.

How out 8th to 11 can be seen are the energy storage E _S1 and / or the optocoupler 30 , in particular the output driver designed as a push-pull output stage 34 of the optocoupler 30 , and / or the FET switching stage 40 dimensioned so that at the exit E1 . E2 of the respective switching unit 12.0 . 12.1 . 12.n . 14.1 . 14.2 . 15 . 16.1 . 16.2 above the measuring resistor R _M for a switch-off pulse, the switch-on time delay and the switch-off time delay are in the range from 450 to 550 ns, and the rise time is in the range from 80 to 120 ns, and the fall time is in the range from 70 to 90 ns.

How out 2 can be seen, form several switching units of which by way of example three switching units 12.0 . 12.1 . 12.n are shown, with corresponding resistors R _1, R _n a tunable high-voltage resistor decade to emulate resistors, which can represent corresponding resistors of ignition circuits. About the switching unit 12.0 For example, an open signal path or the maximum resistance of the high-load resistance decade between the two test connections HS, LS can be represented, the maximum resistance being the drain-source resistance of the FET switching transistors 42 . 44 the switching unit 12.0 in the blocking state corresponds. About the other switching units 12.1 to 12.n can each have a corresponding predetermined replica resistance R ₁ . R _n bridged or short-circuited or looped into the signal path between the two test terminals HS, LS. Depending on the applied control voltage U _S are the two FET switching transistors 42 . 44 activated or switched through, and the output statements E1 . E2 are via the drain-source paths of the two FET switching transistors 42 . 44 short circuited, so that the corresponding tracking resistor R _1, R _n is bridged. Alternatively, the two FET switching transistors 42 . 44 depending on the control voltage U _S locked or opened, so that a current flow through the drain-source paths of the two FET switching transistors 42 . 44 is locked, and the corresponding tracking resistor R _1, R _n into the current path between the test connections HS, LS is looped. In this way, the high-load resistance decade can be dependent on the replica resistors used R ₁ to R _n represent an arbitrarily adjustable resistance range and an interruption.

A further switching unit is used to represent a minimum resistance value or a short circuit between the two test connections HS, LS 15 used, which inserts a minimum resistance value or a maximum resistance value into the signal path between the two test connections HS, LS. The minimum resistance corresponds to a drain-source resistance of the FET switching transistors 42 . 44 in the conductive state. The maximum resistance corresponds to a drain-source resistance of the FET switching transistors 42 . 44 in the blocking state, the first switching unit representing the interruption or the maximum resistance 12.0 the high-load decade is open at the same time.

Via another switching unit 14.1 can the first test connection HS with a first reference potential B1 get connected. Another switching unit 14.2 is used to connect the first test connection HS to a second reference potential GND2, here to the second ground potential. Another switching unit becomes analog 16.1 used the second test terminal LS with a third reference potential B2 connect to. Another switching unit 16.2 can connect the second test connection LS to a fourth reference potential GND2, here to the second ground potential.

Through the different switching units 12.0 to 12.n . 14.1 . 14.2 . 15 . 16.1 . 16.2 can be emulated in an advantageous manner, the real properties of ignition circuits for personal protective equipment. So can the tunable high-load resistor decade 12.0 to 12.n used to simulate resistors in airbag ignition circuits. Furthermore, via the switching unit 15 configurable switch-on periods and / or switch-off periods can be generated and made available, which can be set via time or voltage criteria in order to be able to simulate a real behavior of airbag ignition circuits. Besides, about the switching units 14.1 . 14.2 . 16.1 . 16.2 Short circuits or shunts of the output connections or test connections HS, LS to different potentials B1 . B2 , GND2 be realized. To simulate bounce and loose contacts can via the switching unit 15 and the high-voltage resistance decade 12.0 to 12.n Interrupts and adjustable resistors with adjustable time duration can be specified.

How out 4 can also be seen, includes the pulse generator 50 , a signal generator 52 and an amplifier stage 54 , The signal generator 52 generated in response to the control signal S1 a pulse shape with a corresponding time course. The amplifier stage, which is a transistor T _B , a resistance R _B and a capacitor C _B includes, minimizes the required drive power and shortens the rising or falling edges of the generated control voltage U _S , By dimensioning a series resistor accordingly R _V can control the amplitude of the control voltage U _S can be varied and the FET relay 20 can also be controlled with other voltage levels. The series resistor R _V is between the connection of the first supply voltage U _V1 and a first output terminal of the pulse generator 50 looped in, which with a corresponding first input connection of the FET relay 20 connected is. An output of the amplifier stage 54 is with a second output connector of the pulse generator 50 connected, which with a corresponding second input terminal of the FET relay 20 connected is.

How out 5 can be seen for each FET relay 20 a DC / DC converter 60 used to from the first supply voltage U _V1 the higher second supply voltage U _V2 to supply the FET relay 20 to create. The capacitors are used here E _S1 and E _S2 as energy storage. The condenser E _S1 serves as an energy store to the gate capacitances of the two FET switching transistors 42 . 44 to be able to charge quickly in order to be able to implement the short switching times.

Embodiments of the present invention can replace electromechanical relays or semiconductor relays (solid-state relays) and emulate extremely short interruptions or low-resistance short-circuits in the single-digit microsecond range on control devices to be checked, which are prescribed in the LV124 specification for checking personal protection systems. With electromechanical relays or known semiconductor relays, switching times in the three-digit microsecond range can currently only be achieved. Embodiments of the present invention advantageously enable the requirements in the LV124 specification for checking personal protection means to be met, in which, for example, interruptions in control unit pins are required down to the single-digit microsecond range. With embodiments of the FET relay according to the invention, it is possible to implement switching times under one microsecond. The special design also makes it possible to switch AC loads. By selecting a suitable optocoupler that can quickly charge the gate capacitors of the output stage transistors, it is possible to display currents in the two-digit amp range with very short switch-on times, which are less than one microsecond. At the same time, very low switch-on resistances in the range of approx. 15 mΩ can be made available. Due to the potential separation of the load circuit and the control circuit, just as with electromechanical relays or solid-state relays, it is possible to arrange several FET relays in any combination.

Claims (10)

FET relay having an optocoupler (30) as a control circuit and a FET switching stage (40) as a load circuit, which comprises two FET switching transistors (42, 44), wherein the optocoupler (30) has a coupling stage (32), which in dependence from an on the coupling stage (32) applied control signal (U _S ) an output driver (34) for driving the FET switching stage (40) drives, characterized by an energy store (E _S1 ) for powering the output driver (34) of the optocoupler (30) which, in order to reduce the turn-on times, quickly charges gate capacitances of the FET switching transistors (42, 44) of the FET switching stage (40) via the output driver (34) designed as a push-pull output stage, the output driver (34) of the opto-coupler (30) designed as a push-pull output stage ) quickly discharges the gate capacitances of the FET switching transistors (42, 44) of the FET switching stage (40). FET relay after Claim 1 , characterized in that the FET switching transistors (42, 44) are designed as N-channel field effect transistors or P-channel field effect transistors. FET relay after Claim 1 or 2 characterized in that the source connections (S) of the two FET switching transistors (42, 44) are connected to one another and provide a common reference potential, the gate connections (G) of the two FET switching transistors (42, 44) 44) are connected to one another and can be controlled simultaneously by the output driver (34), and the drain connections (D) of the two FET switching transistors (42, 44) each have an output connection (E1, E2) of the FET relay (20) form which can be connected to a load circuit regardless of polarity. FET relay according to one of Claims 1 to 3 , characterized in that the energy store (E _S1 ) and / or the optocoupler (30) and / or the FET switching stage (40) are dimensioned such that at the output (E1, E2) at a switch-on the turn-on delay in the range of 250 to 350ns, and the turn-off time delay is in the range of 450 to 550ns, and the rise time is in the range of 80 to 120ns, and the fall time is in the range of 70 to 90ns. FET relay according to one of Claims 1 to 4 , characterized in that the energy store (E _S1 ) and / or the optocoupler (30) and / or the FET switching stage (40) are dimensioned such that at the output at a turn-off, the turn-on delay (E1, E2) and the turn-off delay in Range are from 450 to 550ns, and the rise time is in the range of 80 to 120ns, and the fall time is in the range of 70 to 90ns. Test module for testing electrically controllable circuit breakers with an evaluation and control unit (3), a measuring unit (5) and a replica assembly (10), wherein the evaluation and control unit (3) the replica assembly (10) in response to outputs of the measuring unit ( 5) and controls to set certain electrical characteristics at test leads (HS, LS) of the replica assembly (10), characterized in that the replica assembly (10) for adjusting the electrical characteristics at the test leads (HS, LS) comprises at least one FET Relay (20) according to one of Claims 1 to 5 includes. Test module after Claim 6 , characterized in that each FET relay (20) is combined with a pulse generator (50) to form a switching unit (12.0, 12.1, 12.n, 14.1, 14.2, 15, 16.1, 16.2), the pulse generator (50) in Depending on a control signal (S1), a control voltage (U _S ) is generated with a predetermined time profile for controlling the FET relay (20). Test module after Claim 7 , characterized in that a first switching unit (12.0, 12.1, 12.n) bridges a predetermined simulation resistor (R ₁ , R _n ) or loops into a signal path between the two test connections (HS, LS) or the signal path between the two test connections ( HS, LS). Test module after Claim 7 or 8th , characterized in that a second switching unit (15) introduces a minimum resistance value or a maximum resistance value into a signal path between the two test terminals (HS, LS), the minimum resistance being a drain-source resistance of the FET switching transistors (42, 44 ) in the conductive state, and wherein the maximum resistance corresponds to a drain-source resistance of the FET switching transistors (42, 44) in the blocking state. Test module according to one of the Claims 7 to 9 , characterized in that a third switching unit (14.1) connects a first test connection (HS) to a first reference potential (B1) and / or a fourth switching unit (14.2) connects the first test connection (HS) to a second reference potential (GND2) and / or a fifth switching unit (16.1) connects a second test connection (LS) to a third reference potential (B1) and / or a sixth switching unit (16.2) connects the second test connection (LS) to a fourth reference potential (GND2).

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